Fluid bed chlorination of phthalonitriles

ABSTRACT

1. A PROCESS FOR THE PRODUCTION OF A CHLORINATED PHTHALONITRILE WHICH PROCESS COMPRISES: (A) INTRODUCING GASEOUS CI2 AND A MOLTEN, ATOMIZED PHTHALONITRILE INTO A FLUIDIZED BED OF ACTIVATED CARBON PARTICLES MAINTAINED AT A TEMPERATURE WITHIN THE RANGE OF 300* TO 400* C., AT LEAST THE MAJORITY OF THE CHLORINE BEING SEPARATELY INTRODUCED TO THE BOTTOM OF, AND SERVING TO FLUIDIZE, THE BED, THE PHTHALONITRILE, TO GETHER WITH ANY REMAINING CI2, BEING INTRODUCED TO THE BED ABOVE THE POINT OF INTRODUCTION OFF SAID MAJORITY OF CI2; (B) REACTING SAID CI2 AND PHTHALONITRILE THEREIN TO THE DESIRED CHLORINATED PHTHALONITRILE; (C) SEPARATING AND RECOVERING THE RESULTANT CHLORINATED PHTHALONITRILE; AND (D) RECOVERING SOLIDIFIED, PARTICULATE, CHLORINATED PHTHALONITRILE.

Oct. 1,- 1974 ER ET AL 3,839,401

FLUID BED CHLORINATION 0F PHTHALONITRILES Filed Oct. 17. 1972 mwmmamuw zmzjmammo mohzum United States Patent 3,839,401 FLUID BED CHLORINATION OF PHTHALONITRILES Edgar A. Lavergne, North Madison, and Frank S. Mahne, Painesville, Ohio, assignors to Diamond Shamrock Corporation, Cleveland, Ohio Filed Oct. 17, 1972, Ser. No. 298,348 Int. Cl. C07c 121/56 U.S. Cl. 260465 G 14 Claims ABSTRACT OF THE DISCLOSURE A phthalonitrile is liquified and fed to a fluid bed reactor wherein it mixes and reacts with gaseous chlorine in the presence of activated carbon. The resultant chlorinated phthalonitrile is then generally desublimed with CCl and recovered. Treatment of the residual gas, resulting in recovery of HCl and recycle of unreacted C1 is also described. Exemplary is the chlorination of isophthalonitrile to tetrachlorophthalonitrile.

BACKGROUND OF THE INVENTION The various chlorinated phthalonitriles are extremely useful for their biological activity, as is disclosed, for example, in U.S. Pat. No. 3,290,353. In addition to the methods described in that patent, such materials are typically prepared by the vapor phase reaction of one of the isomeric phthalonitriles with C1 in the presence of a catalyst layer, as described in U.S. 3,108,130. While this latter method has seen commercial use when moditied for fluid bed operation, a number of disadvantages obtain relating to decomposition of the organic feed at the temperatures required for vaporization, relatively poor conversion efliciencies, equipment corrosion, reactor and feed line fouling from premature reaction of the feed mixture and the like. Since the biological efficacy of chlorinated phthalonitriles dictates quantity usage, an efiicient process for their production is required.

STATEMENT OF THE INVENTION Therefore, it is an object of the present invention to provide a process, simple of maintenance, for the etficient chlorination of phthalonitriles.

It is a further object of the invention to provide a fluid bed process for the production of chlorinated phthalonitriles.

A still further object of the invention is to provide such a process wherein recovery and recycle of unreacted chlorine is readily possible.

These and other objects will become apparent to those skilled in the art from the specification and claims which follow.

There has now been found a process for the production of a chlorinated phthalonitrile which process comprises:

(a) introducing gaseous C1 and a molten, atomized, phthalonitrile into a fluidized bed of activated carbon particles maintained at a temperature within the range of 300 to 400 C., at least the majority of the chlorine being separately introduced to the bottom of, and serving to fluidize, the bed, the phthalonitrile being introduced to the bed above the point of C1 introduction;

(b) reacting said C1 and phthalonitrile therein to the desired chlorinated phthalonitrile;

(c) removing as a gaseous stream the reaction products,

by-produets, and unreacted materials;

(d) contacting said gaseous stream with a quantity of liquid CCL; sufiicient to desublime substantially all of the chlorinated phthalonitrile while vaporizing substantially all of the CCl and (e) recovering solidified, particulate, chlorinated phthalonitrile.

Patented Oct. 1, 1974 'ice Further, the gaseous stream remaining after desublimation may be scrubbed to remove residual solids, cooled to recover CCL; and separated into HCl and C1 the latter being recycled to the reactor.

The advantages following from the foregoing process are numerous. Feeding a molten, rather than the more conventional vaporous, phthalonitrile substantially reduces loss by decomposition since, in the case of isophthalonitrile for example, a temperature diiferential of about 100 C. is involved. Substantially separate feed of C1 and phthalonitrile materially reduces distributor plate pluggage by prematurely chlorinated materials. Desublimation with C01 which is chemically inert in the process, eliminates the corrosion problems attendant water in the presence of HCl. Further, water, the prior desublimation medium, tends to hydrolyze the chlorinated product, therefore lowering its pH to often unacceptable levels. Recycle of unreacted C1 is an alternative, obviously more attractive than the caustic absorption often practiced, allowing increased chlorine efficiency.

BRIEF DESCRIPTION OF THE DRAWING The Figure is a schematic representation of a process of the present invention including recovery and recycle of unreacted chlorine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the invention for the sake of convenience is described by reference to the chlorination of isophthalonitrile to tetrachloroisophthalonitrile, it will be understood that the term phthalonitrile contemplates that (ortho)phthalonitrile or terephhalonitrile may also be the reactant, with appropriate temperature variation to account for the diiference in melting points, and by adjustment of the Clyphthalonitrile feed ratio, a lower chlorinated material, such as a dichlorophthalonitrile may be obtained.

Referring to the Figure, solid isophthalonitrile is introduced via line 1 to the melter 3 wherein it is heated to in excess of its melting point, e.g., l210 C. The molten isophthalonitrile is pumped through line 5 t0 the fluid bed reactor 7 maintained at a temperature between 330 and 370 C. by means of external jacketing and/or internal cooling means (not shown). It should be noted here that the isophthalonitrile must be introduced into the reactor in a finely divided (atomized) form and that this can be accomplished, for example, either with an appropriate nozzle or by means of a gas as described below.

The major portion, e.g., 90%, and sometimes all of the vaporized C1 is fed preheated to about the same temperature as the isophthalonitrile, via line 9 to the bottom of reactor 7 wherein it passes through the distributor plate into the bed, fiuidizing the activated carbon particles of which the bed is comprised. The molar ratio of Cl zisophthalonitrile employed is within the range of 48:1, preferably 5.0-6.7: 1. Obviously, C1 must be fed at a rate sufficient to maintain the carbon particles in a fluidized state, -a value varying with reactor size and configuration, but generally corresponding to a superficial velocity of 0.2-0.6 foot per second.

If less than the entire amount of C1 is fed to the reactor 7 through line 9, the balance, generally about 10% or less, is diverted by means of a valve through line 11 and then into line 5 where it mixes with and so disperses the molten isophthalonitrile as to atomize same before injection into the lower portion of the fluidized bed above the distributor plate. It is preferable that this mixing takes place as near the reactor as possible in order to reduce the residence time of the mixture in line 5 and prevent premature reaction.

Rather than divert a portion of the C1 to line 5, and should it still be necessary to atomize the isophthalonitrile, an inert gas, such as N or HCl, may be employed in equivalent amounts to the same end. Such a practice is usually less desirable however, since eventual separation from the C1 is required.

Following an average reactor residence time of to 40 seconds, the gases, consisting of tetrachloroisophthalonitrile, unreacted C1 HCl, and minor amounts of isophthalonitrile, are passed via line 13 to the desublimer 15 wherein they are contacted, preferably, with a spray of liquid CCL, introduced via line 17, conveniently at ambient temperature. The amount of CCl., employed should be that required to reduce the product temperature to the point of solidification (desublimation). Use of an excess will result in the desired presence of liquid CCl in the product. Obviously this quantity will vary with temperature and production rate, an amount within the range of 1.5 to 2.5 pounds per pound of product being typical. In this manner, the product, for example, tetrachloroisophthalonitrile, may be directly recovered through line 19 at a high degree of purity (e.g., 97%

Exiting from the desublimer 15 is a gaseous stream comprising C1 HCl, CCl and small amounts of isophthalonitrile and tetr-achloroisophthalonitrile, any entrained solids being removed by means of a bag filter 21. This gaseous stream is conveyed via line 23 to scrubber 25 wherein large amounts of liquid CCl impinge thereon, thus removing the last traces of organics, unreacted or not. Flow from scrubber 25 via line 26 into holding vessel 27 results in a body of liquid CCL, that may be allowed to become saturated with organics. This saturated CCl is drawn from holding vessel 27 through line 28, filtered, with solids disposed of through line 29, and recycled to the scrubbing operation, through -a heater, via line 31. Alternatively, a portion of the (generally less than saturated) liquid may be drawn through line 28 to an evaporator (not shown) wherein the C01 may be distilled 01f, cooled, and recycled through line 31. Since the scrubbing efiiciency is inversely proportional to the degree of CCl saturation, treatment of the CCL, in the holding vessel 27 should be varied as required. The CCL, used for the actual scrubbing is preferably at a temperature of about 65 C. (i-S"). A somewhat lower temperature, about 50 C., obtains in the holding vessel owing to recycle of cooled CCL, from a later stage.

The gases exiting through line 33 now contain only C1 -HC1, and CCl the latter of which is removed by cooling to about -6 C. and recycled via line 35 to holding vessel 27. In the final separator stage 37, C1 and HCl are separated, HCl being removed via line 39 and C1 recycled through line 41 to line 9 wherein it is combined with vaporized chlorine as a reactor feed. Chlorine may be separated by cyclic absorption and desorption as is known in the art.

Although it is possible to apply pressure to drive the gases from the desublimer through the Cl /HCl separation stage, more desirably a slight vacuum, e.g., a negative pressure of 2 to inches of water, is employed.

While reference has been made exclusively to the chlorination of isophthalonitrile to tetrachloroisophthalonitrile, with minor alterations reflecting the diflerences in physical properties of the isomers, the process applies as well to the production of tetrachlorophthalonitrile. For example, (ortho)phtha1onitrile, having a lower melting point, may be heated in melter 3 to a temperature of 150 C. to 170 C. for feed to reactor 7 operating at 300 to 400 C. On the other extreme, the higher melting terephthalonitr-ile requires melter temperatures of 235 to 250 C. As indicated, lower chlorinated materials are possible if the ratio of chlorine to organic is reduced. For example, at a molar ratio of 2.0 to 2.5 :1. a substantially dichlorophthalonitrile product is obtained.

In order that those skilled in the art may more readily 4 understand the present invention and certain preferred embodiments by which it may be carried into elfect, the following specific example is afforded.

EXAMPLE Reference is made to the attached Figure where necessary. Technical grade isophthalonitrile (purity 97%) is fed to the melter 3 wherein it is heated to 200 C. and then pumped to the reactor 7 at a rate of 100 lbs/hr. Chlorine, preheated to 20 C., enters the reactor at a rate of 325 lbs./hr., an amount giving a Cl :isophthalo nitrile mole ratio of 5.4: 1. The majority of said chlorine enters the bottom of the reactor and passes through the distributor plate, fluidizing a bed of activated carbon having a particle size range of 100-300 microns, then mixes and reacts with the separate feed of isophthalonitrile (which is atomized with 5% of the C1 feed) at a temperature of 350 C., said temperature being maintained by means of an oil jacket.

The gases exiting from the reactor are contacted in the desublimer 15 with a spray of 0.4 gallon/minute CCl at a temperature of 20 C., whereupon a particulate product is recovered from the bottom having an analysis of greater than 97% tetrachloroisophthalonitrile and less than 0.5 unreacted isophthalonitrile.

The remaining gases pass to a scrubber 25 wherein a spray of 15 lbs. CCl per pound of gas, at a temperature of 65 C. removes the residual tetrachloroisophthalonitrile and unreacted isophthalonitrile, the result being a saturated solution which is filtered to remove solids prior to recycle through the scrubber.

The gas stream now consists of C1 HCl, and CCl the latter of which is removed by cooling to 6 C. and recycled to the scrubber.

The chlorine and HCl are now passed through liquid CCl which acts to absorb the C1 the HCl then being absorbed in water. Finally, the C1 is stripped from the C1 for recycle to the reactor.

The overall isophthalonitrile efiiciency is determined to be 94%. The process operates with a minimum of down time for reactor cleaning. Desublimer corrosion is not found.

While the invention has been described by reference to certain preferred embodiments thereof, it is not to be so limited, as will be apparent from the scope of the appended claims.

We claim:

1. A process for the production of a chlorinated phthalonitrile which process comprises:

(a) introducing gaseous C1 and a molten, atomized, phthalonitrile into a fluidized bed of activated carbon particles maintained at a temperature within the range of 300 to 400 C., at least the majority of the chlorine being separately introduced to the bottom of, and serving to fluidize, the bed, the phthalonitrile, together with any remaining Cl being introduced to the bed above the point of introduction of said majority of C1 (b) reacting said C1 and phthalonitrile therein to the desired chlorinated phthalonitrile;

(c) separating and recovering the resultant chlorinated phthalonitrile; and

(d) recovering solidified, particulate, chlorinated phthalonitrile.

2. A process as in Claim 1 wherein the molten phthalonitrile is isophthalonitrile and is introduced at a temperature of about 190 to 210 C.

3. A process as in Claim 1 wherein to of the C1 is introduced to the bottom of the bed.

4. A process as in Claim 1 wherein the mole ratio of C1 to phthalonitrile fed is 5.06.7: 1.

5. A process as in Claim 1 wherein any balance of the C1 not separately introduced is mixed with molten phthalonitrile immediately prior to introduction into the bed and serves to atomize same.

6. A process as in Claim 1 wherein the reaction is at a temperature between 330 and 370 C.

7. A process for the production of a chlorinated phthalonitrile which process comprises:

(a) introducing gaseous C1 and a molten, atomized, phthalonitrile into a fluidized bed of activated carbon particles maintained at a temperature within the range of 300 to 400 C., at least the majority of the C1 being separately introduced to the bottom of, and serving to fluidize, the bed, the phthalonitrile, together with any remaining C1 being introduced to the bed above the point of introduction of said majority of C1 (b) reacting said C1 and phthalonitrile therein to the desired chlorinated phthalonitrile;

(c) removing as a gaseous stream the reaction products,

by-products, and unreacted materials;

(d) contacting said gaseous stream with a quantity of liquid CCl sufficient to desublime substantially all of the chlorinated phthalonitrile while vaporizing substantially all of the CCl.,.

8. A process as in Claim 7 wherein the temperature of the liquid CCL; in the desublimation step is ambient.

9. A process as in Claim 7 wherein the phthalonitrile is isophthalonitrile and the product is tetrachloroisophthalonitrile.

10. A process for the production of a chlorinated phthalonitrile which process comprises:

(a) introducing gaseous C1 and a molten, atomized, phthalonitrile into a fluidized bed of activated carbon particles maintained at a temperature within the range of 300 to 400 C., at least the majority of the C1 being separately introduced to the bottom of, and serving to fluidize, the bed, the phthalonitrile, together with any remaining C1 being introduced to the bed above the point of introduction of said majority of C1 (b) reacting said C1 and phthalonitrile therein to the desired chlorinated phthalonitrile;

(c) removing as a gaseous stream the reaction products,

by-products, and unreacted materials;

(d) contacting said gaseous stream with a quantity of liquid CCL; sufficient to desublime substantially all of the chlorinated phthalonitrile while vaporizing substantially all of the CCl (e) recovering solidified, particulate, chlorinated phthalonitrile;

(f) removing a gaseous stream containing unreacted C1 HCl, CCl and small amounts of phthalonitrile and chlorinated phthalonitrile from the desublimer;

(g) scrubbing said gaseous stream with liquid C01 to remove the phthalonitrile and chlorinated phthalonitrile;

(h) cooling the resultant gaseous stream containing CCl C1 and I-ICl to remove said CC]; and

(i) separating the HCl from the C1 11. A process as in Claim 10 wherein the C1 from step (i) is recycled to step (a).

12. A process as in Claim 10 wherein the liquid CCl used to scrub the gaseous stream is at a temperature of from to C.

13. A process as in Claim 10 wherein steps (d) through (i), except (e), are conducted at a negative pressure of 2 to 30 inches of water.

14. A process for the production of tetrachloroisophthalonitrile which process comprises:

(a) introducing gaseous C1 and molten, atomized, isophthalonitrile at a temperature of about 200 C. into a fluidized bed of activated carbon particles maintained at a temperature of about 350 C., about of the C1 being separately introduced to the bottom of, and serving to fluidize, the bed, the isophthalonitrile and the remaining C1 being introduced to the bed above the point of C1 introduction;

(b) reacting the Cl; and isophthalonitrile therein to the desired tetrachloroisophthalonitrile;

(c) removing a gaseous stream consisting essentially of tetrachloroisophthalonitrile, HCl, C1 and unreacted isophthalonitrile;

(d) contacting said gaseous stream with a quantity of liquid CCl at about ambient temperature, sufiicient to desublime substantially all of the tetrachloroisophthalonitrile while vaporizing substantially all of the CCl (e) recovering solidified particulate tetrachloroisophthalonitrile;

(f) removing from the desublimer a gaseous stream consisting essentially of HCl, C1 CCl and small amounts of isophthalonitrile and tetrachloroisophthalonitrile;

(g) scrubbing said gaseous stream with liquid CCl at about 65 C. to remove the remainder of isophthalonitrile and tetrachloroisophthalonitrile;

(h) cooling the resultant gaseous stream to condense and recover CCl (i) separating the C1 and HCl; and

(j) recycling the C1 from step (i) to step (a).

References Cited UNITED STATES PATENTS 3,108,130 10/1963 Haga et a1 260465 LEWIS GOTTS, Primary Examiner D. H. TORRENCE. Assistant Examiner UNITED S'I ATES PATENT OFFICE- CERTIFICATE OF CORRECTION Patent No. 3;, 839,401 Dated October 1, 1974 I nventor(s A Edgar A. Lavergne and Frank S. Mahne It .is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I Col. 5, line 16; cancel "desired", substitute --undesir 'ed--. I v Col. 4, line-39 cancel "C1 substitute -CC1 signedma seal d this 3rd day ofDeeember 3.974.

(SEAL) v Attes t McCOY M. GIBSON JR. I V c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) UscMM Dc 6o37 p9 I n u.s. eoviermnsm' PRINTING OFFICE u" o-an-su. 

1. A PROCESS FOR THE PRODUCTION OF A CHLORINATED PHTHALONITRILE WHICH PROCESS COMPRISES: (A) INTRODUCING GASEOUS CI2 AND A MOLTEN, ATOMIZED PHTHALONITRILE INTO A FLUIDIZED BED OF ACTIVATED CARBON PARTICLES MAINTAINED AT A TEMPERATURE WITHIN THE RANGE OF 300* TO 400* C., AT LEAST THE MAJORITY OF THE CHLORINE BEING SEPARATELY INTRODUCED TO THE BOTTOM OF, AND SERVING TO FLUIDIZE, THE BED, THE PHTHALONITRILE, TO GETHER WITH ANY REMAINING CI2, BEING INTRODUCED TO THE BED ABOVE THE POINT OF INTRODUCTION OFF SAID MAJORITY OF CI2; (B) REACTING SAID CI2 AND PHTHALONITRILE THEREIN TO THE DESIRED CHLORINATED PHTHALONITRILE; (C) SEPARATING AND RECOVERING THE RESULTANT CHLORINATED PHTHALONITRILE; AND (D) RECOVERING SOLIDIFIED, PARTICULATE, CHLORINATED PHTHALONITRILE. 